Polymeric articles

ABSTRACT

A process for the production of a marker sleeve assembly which comprises deforming a substantially non-cross-linked web of polymeric material at a temperature below the crystalline melting point or softening point of the material to render the web heat-recoverable, fusing together parts of the web or parts of the web and at least one other polymeric web to define a plurality of radially inwardly heat-recoverable marker sleeves, disposed in side-by-side relationship and preferably separable and subsequently cross-linking the resulting assembly.

This application is a division, of application Ser. No. 172,889, filed7/28/80 now U.S. Pat. No. 4,349,404.

The present invention concerns heat-recoverable polymeric articles, thatis to say, articles the dimensional configuration of which may be madeto change by subjecting to heat, and in particular, to such articles foruse as identifying markers and to a process for their manufacture.

Identifying markers are frequently employed for identifying thecomponents of complicated equipment particularly complex electricalequipment, for example complex wiring systems in aircraft. One suchmarker system has taken the form of an assembly of heat-recoverablesleeves which may be marked in any manner and which may be slipped overthe component to be identified and heat-recovered thereon. Such assemblycomprises an elongate spine provided on one side thereof with aplurality of transversely extending spaced apart support bars on each ofwhich is disposed a heat-recoverable marker sleeve. Such an assemblyfacilitates marking and sequencing of the marker sleeves and ifnecessary furthermore enables the marker sleeves to be subjected to heattreatment to fix or render permanent the markings on the sleeve withoutrisk of premature heat-recovery.

Whilst such marker sleeve assembly has many attributes, the manufacturethereof is complex. The marker sleeves are manufactured from polymerictubing which is rendered heat recoverable by cross-linking the tubing,heating the tubing to a temperature above the crystalline melting pointor softening point of the polymeric material, deforming the tuberadially outwardly and cooling the tubing in the deformed state. In use,since the deformed state of the article is heat unstable, application ofheat will cause the tubing to revert to the original heat stableconfiguration. The tubing so produced is cut down into a plurality ofshort sleeves each of which are then individually disposed on thesupport bars of the elongate spine and located thereon by slight heatrecovery, the sleeves so located still retaining a substantial residualamount of heat recovery.

The present invention has as an object to provide a process for theproduction of an alternative type of heat-recoverable marker sleeveassembly which is less complex than that hitherto employed.

Accordingly, the present invention provides a process for the productionof a marker sleeve assembly which comprises deforming a substantiallynon-cross-linked web of polymeric material at a temperature below thecrystalline melting point or softening point of the material to renderthe web heat-recoverable, fusing together parts of the web or parts ofthe web and at least one other polymeric web to define a plurality ofradially inwardly heat-recoverable marker sleeves, disposed inside-by-side relationship and preferably separable and subsequentlycross-linking the resulting assembly.

By the expression "fusing together" as employed herein is meant aprocess wherein the materials in the parts to be fused together arecaused to flow together, e.g. welding by heat, solvent, or ultrasonic orradio frequency energy, preferably with the application of pressure, toform a homogeneous bridge between the parts in the absence of anydiscernible interface therebetween.

The fusion step may be effected before or after deformation, preferablyhowever after deformation.

Preferably, the marker sleeve assembly is produced in a "tear-off"arrangement being provided with lines of weakness, e.g. perforations,facilitating separation and removal of individual marker sleeves fromthe assembly, as required.

The marker sleeves may be provided with identifying characters or othermarkings at any stage in the production process, e.g. on the polymericweb before or after the fusing step. Alternatively, the sleeves may beproduced devoid of identifying markings, these to be provided by theuser, e.g. by a typing operation.

In a first preferred form of the invention, the assembly is producedfrom at least one pair of longitudinally expanded non-cross-linkedpolymeric sheets which are superimposed and welded together laterallythereof at longitudinally spaced apart intervals. Preferably the weldseams defining the laterally extending marker sleeves are provided withlines of weakness, e.g. are perforated to facilitate separation of thesleeves.

If it is desirable to enable individual marker sleeves to be removed outof sequence without disturbing the sequence of the remaining sleeves,then provision may be made for a retaining spine along one edge of theassembly. For example the assembly may be provided with a longitudinallyextending line of weakness, the marker sleeves so being bounded by onefree edge, the welded seams and said longitudinally extending line ofweakness. In such case, said line of weakness may comprises a series ofslits, each slit extending across the width of the marker sleeves, thewelded seams forming a bridge between the sleeves and the spine. In suchcase also, one sheet may advantageously be wider than the other of theor each pair of sheets, the spine in such case consisting of the oneedge region of the wider sheet.

In such first preferred form, said pair(s) of polymeric sheets may beattached to a non-heat-recoverable support means to restrainheat-recovery of the marker sleeves under heat treatment to fix orrender permanent markings on the sleeves. Such support means maycomprise a strip to which, or, to each side of which, a pair ofpolymeric sheets as hereinbefore described may be secured, at least atthe extremities thereof.

In a second preferred form of the invention, the assembly is producedfrom a single longitudinally expanded sheet which is folded laterallythereof at spaced apart intervals and welded laterally along the base ofeach fold to provide a plurality of spaced apart laterally extendingmarker sleeves. Preferably in such form also, perforations are providedalong the weld seams to facilitate removal of the sleeves. Such form hasthe advantage that sleeves may be removed at any position in theassembly permitting the assembly to remain otherwise intact.

In a third preferred form of the invention, the assembly is producedfrom at least one pair of longitudinally expanded non-cross-linkedpolymeric sheets which are superimposed onto at least one side of anon-expanded polymeric support strip said pair of sheets being weldedtogether and to the support strip laterally of the sheets atlongitudinally spaced apart intervals. Preferably the weld seamsdefining the laterally extending marker sleeves are perforated tofacilitate their separation. Such third preferred form has the advantagethat sleeves at any position in the assembly may be removed whilstpermitting the assembly otherwise to remain intact.

Further, by appropriate choice of support strip material the assemblymay be subjected to heat treatment to fix or render permanent theidentifying markings on the sleeves, without causing the sleeves toloose their heat-recovery, e.g. by choice of a support strip materialthat remains semi-rigid at the heat treatment temperature. When asupport strip is employed, a pair of expanded polymeric sheets may bewelded to each face thereof to provide marker sleeves on both faces.

The assembly may be provided longitudinally thereof with a plurality ofindexing slots or apertures adapted to be engageable with the teeth of asprocket mechanism to be advanceable through a printer, e.g. atypewriter, and so facilitate marking. For example in the case where theassembly is provided with a longitudinally extending exposed spine orsupport strip, the indexing slots or apertures may be provided in saidspine or strip.

The process is applicable to both crystalline and non-crystallinepolymers, the crystalline melting point or softening point beingselected accordingly as the maximum deformation temperature.

By "substantially non-cross-linked" polymeric materials as employedherein is meant not cross-linked to the extent that the material cannotbe readily bonded to itself or to another polymeric component by fusing.In general, the level of cross-linking in the polymeric materialexpressed in terms of gel content (ANSI/ASTM D2765-68) is preferablyless than 40%, more preferably less than 20%, particularly less than 5%.When cross-linking in accordance with the process, preferably gelcontents of at least 40%, e.g. at least 50%, particularly at least 65%are attained.

Marker sleeves and a marker sleeve assembly produced by the process ofthe invention also form part of the present invention.

One advantage of the marker sleeves of the invention is that they aresubstantially recoverable, e.g. recoverable to at least 50% of theirmaximum extent, at a temperature below the crystalline melting point orsoftening point of the polymeric material from which they have beenproduced, e.g. in the range 60° C. to the crystalline melting point orsoftening point.

Any cross-linkable polymeric material to which the property ofdimensional recoverability may be imparted such as those disclosed in UKspecification No. 990,235 may be used to form the articles. Polymerswhich may be used in the polymeric material include polyolefins such aspolyethylene and polypropylene, and ethylene copolymers, for examplewith propylene, butene, hexene, octene, vinyl acetate or other vinylesters or methyl or ethyl acrylate, polyamides, polyurethanes, polyvinylchloride, polyvinylidine fluoride, or other fluorinated polymers orcopolymers, e.g. Tefzel (trade name--commercially available fromDupont), elastomeric materials such as those disclosed in UKspecification No. 1,010,064 and blends such as those disclosed in UKspecification Nos. 1,284,082 and 1,294,665, and compositions such asthose disclosed in our co-pending Application Nos. 15122/77 and37468/78. The polymeric materials can be tailored to suit the intendeduse by the addition of fillers or other additives, e.g. flameretardants, plasticisers, pigments, stabilisers and lubricants.

The polymeric material may be cross-linked by irradiation, for example,by means of an electron beam or by γ-radiation or it may be chemicallycross-linked. Whichever cross-linking process is used, it may beadvantageous to incorporate one or more co-curing agents for examplepolyunsaturated monomers such as triallyl cyanurate, triallylisocyanurate, diallyl phthalate, ethylene glycol dimethacrylate,trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate,allyl methacrylate and vinyl methacrylate. One method of chemicalcross-linking that may be used in the process according to the inventioninvolves grafting an unsaturated hydrolysable silane on the polymer andsubjecting the article to moisture during a curing stage, for example,as described in UK Patent specification Nos. 1,286,460 and 1,357,549.Any of the techniques conventionally employed for fusing togetherpolymeric materials may be employed in the process of the presentinvention, e.g. radio frequency, ultrasonic or hot bar welding, andpressure may additionally be applied to ensure a satisfactory bond.Furthermore, it is possible to make use of the fusing operation toprovide lines of weakness, e.g. perforations between the marker sleevesof the assembly. For example, it is possible to use aheating/perforating device such as a welding tool provided with atoothed wheel, if necessary in association with pressure applying meanssuch as a roller.

The wall thickness of the marker sleeves may vary, e.g. from 0.01 to 3mm prior to heat-recovery, preferably from 0.1 to 1 mm.

Specific embodiments of the process of the invention will now bedescribed by way of example with specific reference to the accompanyingdrawings wherein:

FIG. 1 is a schematic side view of a marker sleeve assembly inaccordance with a first embodiment of the invention,

FIG. 2 shows a section through the assembly of FIG. 1,

FIG. 3 is a side view of a single marker sleeve detached from theassembly of FIG. 1,

FIG. 4 is a schematic side view of a marker sleeve assembly inaccordance with a second embodiment of the invention,

FIG. 5 shows a section through the assembly of FIG. 4,

FIG. 6 is a schematic side view of a single marker sleeve detached fromthe assembly of FIG. 4,

FIG. 7 is a schematic side view of a marker sleeve assembly inaccordance with a third embodiment of the invention,

FIG. 8 shows a section through the assembly of FIG. 7, and

FIG. 9 is a side view of a single marker sleeve detached from theassembly of FIG. 7.

FIG. 10 is a view similar to FIG. 1 showing a modification of the firstembodiment of the invention,

FIG. 11 is a view similar to FIG. 1 showing another modification of thefirst embodiment of the invention, and

FIG. 12 is a view similar to FIG. 7 showing a modification of the thirdembodiment of the invention.

With reference to FIGS. 1, 2 and the marker sleeve assembly of the firstembodiment is produced from a pair of superimposed non-cross-linkedpolyethylene sheets each of which having been deformed by stretching ina longitudinal direction depicted in FIG. 1 by arrow X at a temperatureof 100° C. and allowed to cool in the deformed condition. Thesuperimposed deformed sheets are welded together laterally thereof withan RF welding tool to produce weld seams 2 and define a plurality ofspaced apart marker sleeves 4. The assembly is provided with lines ofweakness in the form of perforations 3 disposed along the weld seams 2to facilitate removal of individual sleeves 4. The assembly isthereafter irradiated with a 1.5 MeV electron beam at a dosage of 12Mrads causing cross-linking of the polyethylene. The assembly of blankmarker sleeves may be provided with appropriate markings, e.g. by use ofa normal typewriter.

The resulting marker sleeve assembly is simply produced yet provides asequenced series of heat-recoverable marker sleeves which may beemployed for identifying purposes in manner known per se.

If it is desirable, as mentioned earlier, to enable individual markersleeves to be removed out of seguence without disturbing the sequence ofthe remaining sleeves, then provision may be made for a retaining spinealong one edge of the assembly, as can be seen in FIGS. 10 and 111. Forexample, the assembly may be provided with a longitudinally-extendingline of weakness, the marker sleeves so being abounded by one free edge,the welded seams, and said longitudinally-extending line of weakness. Insuch case, said line of weakness may comprise a series of slits, eachslit extending across the width of the marker sleeves, the welded seamsforming a bridge between the sleeves and the spine. In such case also,one sheet may advantageously be wider than the other of the or each pairof sheets, the spine in such case consisting of the one edge region ofthe wider sheet as can be seen in FIGS. 10 and 12.

In a modification (not shown) of the first embodiment to enable themarker sleeve assemblies when provided with identifying markings, e.g.from a typewriter, to be subjected to a heat treatment to fix or renderpermanent the markings on the sleeves, each assembly is provided with asupport means in the form of a polymeric non-heat-recoverable polymericstrip which remains at least semi-rigid at the heat treatmenttemperature, attached to at least each extremity of the assembly. Suchattachment may be achieved by the use of mechanical attachment meanse.g. clips, or may be welded to the assembly prior to cross-linking atleast to the terminal sleeves of the assembly.

In the second embodiment illustrated in FIGS. 4, 5, and 6, the assemblyis produced from a single sheet of non-cross-linked longitudinallyexpanded polyethylene sheets, i.e. expanded in the direction indicatedby arrow X in FIG. 4, produced in analogous manner to that described inthe first embodiment, the sheet being transversely folded atlongitudinally spaced apart intervals and each fold being weldedemploying an RF welding tool along the base thereof to produce weldseams 6 and thereby define a plurality of interlinked laterally disposedspaced apart sleeves 7. Between each sleeve 7 so produced and theinterlinking polyethylene sheet along the weld seams 6 are providedlines of weakness in the form of a line of perforations to permit atear-off arrangement and facilitate detachment of individual sleeves.The assembly so produced is subjected to electron irradiation andthereafter provided with identifying characters in analogous manner tothat described in relation to the first embodiment. It is to be notedthat the assembly of the second embodiment permits a marker sleeve to beremoved out of sequence, i.e. from any position in the assembly theassembly otherwise remaining intact.

In the third embodiment illustrated in FIGS. 7, 8 and 9, two pairs oflongitudinally expanded polyethylene sheets 8a and 8b, 8c and 8d (i.e.expanded in the direction indicated by arrow X) each produced inaccordance with the procedure described in relation to the firstembodiment are placed one pair on each side of a non-cross-linkedsemi-rigid polymeric support strip 9 in stacked relationship and eachpair of polyethylene sheets 8a and 8b and 8c and 8d welded together andto each face of the polymeric support strip laterally thereof at spacedapart intervals employing an RF welding tool to produce welded seams 10aand 10b on each side of support strip 9 and to define a plurality oflaterally disposed spaced apart marker sleeves 12 on each side of thesupport strip 9. Each weld seam 10a or 10b is provided with two rows ofperforations in region of the seams not directly integral with thesupport strip to facilitate detachment of the marker sleeves. Therelative width of the support strip 9 and polymeric sheets 8 is suchthat the marker sleeves protrude slightly from one side edge 13 of thesupport strip to provide a convenient securing tab to facilitate removalof the sleeves. The assembly is then subjected to electron irradiationas described in relation to the first embodiment, the assembly thenbeing in a condition to accept markings, e.g. by way of a typewriter andto undergo heat treatment to render permanent the markings. It should benoted that the polymeric material of the support strip 9 is selectedsuch that it will remain sufficiently rigid at the heat treatmenttemperature as to prevent premature heat-recovery of the marker sleeves.

It is to be noted that apart from the allowing heat treatment to renderpermanent markings on the sleeves, the assembly also has a high densityof marker sleeves and permits any marker sleeve to be detached whilstotherwise remaining intact.

In a modification of the third embodiment (not shown), the support stripextends proud of the marker sleeves on the side thereof opposite to side13 to expose one edge region thereof.

Along the edge region so exposed is provided a series of slots orapertures which are adapted to be engageable with the teeth of asprocket mechanism to be advanceable through a printer e.g. a typewriterand so facilitate marking. FIGS. 10 and 11 also illustrate indexingslots or apertures.

We claim:
 1. A marker sleeve assembly of individual, open-ended tubularmarker sleeves detachably joined together, comprising, in combination:afirst sheet and a second sheet of flexible material arranged inface-to-face relationship and having longitudinal axes disposed parallelto one another, the first sheet being transversely wider than the secondsheet such that the first sheet has at least one longitudinal marginaledge portion extending beyond the corresponding longitudinal edge of thesecond sheet; a plurality of spaced transverse seams joining the firstand second sheets together at preselected intervals, the transverseseams being arranged perpendicular to the longitudinal axes of the firstand second sheets, each adjacent pair of transverse seams definingopposed closed edge portions of an individual marker sleeve; andseparable line means defined in the marginal edge portion of the firstsheet, the separable line means being parallel to the longitudinal axisof the first sheet, the separable line means and the adjacentlongitudinal edge of the second sheet defining an open end of a markersleeve, each individual, open-ended tubular marker sleeve beingdetachable from the assembly along said transverse seams and saidseparable line means.
 2. An assembly of individual tubular markersleeves as defined in claim 1, wherein a weakened zone is defined alongeach transverse seam, and each individual marker sleeve is detachablefrom the assembly along a weakened zone.
 3. An assembly of individualtubular marker sleeves as defined in claim 1, wherein a line of weaknessextends along each transverse seam, and an individual marker sleeve ismanually detachable from the assembly along a line of weakness.
 4. Anassembly of individual tubular marker sleeves as defined in claim 1, 2or 3, wherein a row of spaced apertures extends longitudinally withinthe marginal edge portion of the first sheet parallel to thelongitudinal axis of the first sheet.
 5. A marker sleeve assemblycomprising, in combination:a first sheet and a second sheet superposedupon the another, both sheets being of equal width and havinglongitudinal axes arranged parallel to each other; a plurality of spacedtransverse seams joining the first sheet and the second sheet togetherat preselected intervals, the transverse seams being arrangedperpendicular to the longitudinal axes of the first sheet and the secondsheet; and a row of spaced longitudinal slits defined in a marginal edgeportion of the assembly, each said slit extending through the firstsheet and the second sheet and separated from one another by connectinglands comprising portions of the transverse seams, each individualmarker sleeve being manually detachable from the assembly along saidtransverse seams and said longitudinal slits and having opposed closededge portions defined by portions of an adjacent pair of transverseseams and an open end defined by said longitudinal slit.
 6. A markersleeve assembly according to claim 5, further including:a line ofweakness extending along each transverse seam and providing means formanually detaching an individual marker sleeve from the assembly.
 7. Amarker sleeve assembly according to claim 5 or 6, further including:arow of spaced apertures formed in the marginal edge portion of theassembly and extending through the first sheet and the second sheet forengagement with sprocket sheet drive means.